Background
Ascending aortic dilation is important in bicuspid aortic valve disease (BAV), with increased risk of aortic dissection. We used cardiovascular magnetic resonance (CMR) to understand the pathophysiology better by examining the links between 3-dimensional flow abnormalities, aortic function and aortic dilation.
Methods and Results
142 subjects underwent CMR (mean age 40 years; 95 with BAV, 47 healthy volunteers [HV]). BAV patients had predominantly abnormal right-handed helical flow in the ascending aorta, larger ascending aortas (18.3 ±3.3 vs. 15.2 ±2.2mm/m2, p<0.001), and higher rotational (helical) flow (31.7 ±15.8 vs. 2.9 ±3.9mm2/s, p<0.001), systolic flow angle (23.1 ±12.5 vs. 7.0 ±4.6°, p<0.001) and systolic wall shear stress (WSS) (0.85 ±0.28 vs. 0.59 ±0.17N/m2, p<0.001) compared to HV. BAV with right-handed flow and right-non coronary cusp fusion (n= 31) showed more severe flow abnormalities (rotational flow 38.5 ±16.5 vs. 27.8 ±12.4mm2/s, p<0.001; systolic flow angle 29.4 ±10.9 vs. 19.4 ±11.4°, p<0.001; in-plane WSS 0.64 ±0.23 vs. 0.47 ±0.22N/m2, p<0.001) and larger aortas (19.5 ±3.4 vs. 17.5 ±3.1mm/m2, p<0.05) than right-left cusp fusion (n=55). BAV patients with normal flow patterns had similar aortic dimensions and WSS to HV and younger BAV patients showed abnormal flow patterns but no aortic dilation, both further supporting the importance of flow pattern in the etiology of aortic dilation. Aortic function measures (distensibility, aortic strain and pulse wave velocity) were similar across all groups.
Conclusions
Flow abnormalities may be a major contributor to aortic dilation in BAV. Fusion type affects the severity of flow abnormalities, and may allow better risk prediction and selection of patients for earlier surgical intervention.
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